A silicon carbide semiconductor device is a semiconductor device which includes a silicon carbide layer (SiC layer), and has excellent technical features such as a high breakdown voltage, a low loss, a low leakage current, high-temperature operability, and high-speed operability. Accordingly, the application of the silicon carbide semiconductor device to a power element such as a switching element or a rectifying element has been highly anticipated. As the power element, although a power MOSFET, an IGBT, a Schottky diode, a pn diode, a thyristor or the like has been known, all these power elements have an ohmic electrode layer which is in contact with an SiC layer so that, in many cases, an electric current of several amperes flows between the SiC layer and the ohmic electrode layer.
Conventionally, as a method for manufacturing a silicon carbide semiconductor device, there has been known a method described in patent literature 1 (a conventional method for manufacturing a silicon carbide semiconductor device). FIG. 14A to FIG. 14E are views for explaining the conventional method for manufacturing a silicon carbide semiconductor device. FIG. 14A to FIG. 14E are views showing respective steps. The conventional method for manufacturing a silicon carbide semiconductor device sequentially includes, as shown in FIG. 14A to FIG. 14E, an Ni layer forming step where an Ni layer 920 is formed on an SiC layer 910 (FIG. 14A), a high-temperature annealing step where an alloy layer 926 constituted of a reaction layer 922 and a silicide layer 924 is formed on the SiC layer 910 by making the SiC layer 910 and the Ni layer 920 react with each other at a temperature of 950° C. or above ((FIG. 14B and FIG. 14C), an etching step where a surface of the reaction layer 922 is exposed by removing the silicide layer 924 (FIG. 14D), and an electrode layer forming step where an ohmic electrode layer 930 and other electrode layers 932 are formed on a surface of the reaction layer 922 (FIG. 14E) in this order.
According to the conventional method for manufacturing a silicon carbide semiconductor device, carbon components in the SiC layer 910 are not diffused into the ohmic electrode layer 930. As a result, the adhesive property between the ohmic electrode layer 930 and other electrode layers 932 can be improved. Accordingly, it is possible to manufacture a highly reliable silicon carbide semiconductor device which can decrease a possibility of peeling off of an electrode while ensuring a favorable contact between the SiC layer and the electrode layer.